1. Field of the Invention
The invention relates to a screened electric switch containing in a housing two mutually mobile contacts, suitable control devices to open the switch, a mobile screen and the impelling devices designed to move an edge of this screen rapidly between the contacts, in order to shear the arc striking between the parting contacts between this edge and an insulating surface contained in the housing.
It applies namely, but in no way exclusively, to circuit breaking devices designed to open a line where they are in series, either on transient currents, e.g. during short-circuit inception, or on high-level steady-state currents.
2. Description of the Prior Art
Such switches are already known, e.g. in French patent application No. 83 01749 of Feb. 4, 1983 filed by the Applicant. If the means implemented to cause screen movement are not suitable for the increase rate or the rating of the current to be interrupted, the same quality breaking may not be obtained in each one of the situations where breaking is required.
Hence the purpose of the invention is to provide this type of known switches with suitable means to tailor the screen motion velocity to the energy released by the arc at the moment it strikes between the contacts.